The blow off valve issue - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Dustyx77 · 09-08-2020, 07:10 AM

Hey guys, sooo I've bought a 200sx (eurospec) s14 that used to run on 24psi of boost, but the blow off valve, atleast according to the internet, is rated for 26psi. Sooo long story short, the car has still some major compressor surge sounds. I barely use full throttle because I use the car on the street. What kind of psi blow off valve spring would you guys suggest?

S14rebuild · 09-13-2020, 06:39 AM

If ur getting surge then the bov isnt opening or its too small.

First check your vacuum line to it. Should be a direct feed from intake manifold to the bov, not "teed" off another line.

Then make sure it acually opens, not stuck or damaged.

*TheRealSy90* · 09-14-2020, 10:48 AM

Your bov is probably set stiff so that it only fully opens if you were at full boost, and anything under that when cruising around it just stays closed.

Kingtal0n · 12-16-2020, 09:27 PM

The correct type of bypass for a turbo will hang open at idle, like the stock bov.

The best thing for the turbo is to be able to instantly relief any air, from using a very easy to open bov style.

The reason people don't like to use the correct type of bov on their cars is often because they do not have a recirculated bov style.
In other words, you need the bov to recirculate the air back to the intake (pre turbo) just like FACTORY does, or else, the maf will dump extra rich fuel into the engine whenever the bov opens.

I suggest looking at the factory bov setup, the bypass style. See if you can get a BYPASS style bov. For example greddy type-s was a bypass style bov.
Always put the bov as close to the turbo as possible. Never put it after an intercooler either.

If you get bypass style bov, you can use a very easily to open bov, so the turbo will never be in *pain*.
If you cannot get the bypass style, then the best alternative solution (used to be) is HKS SSQV placed right near the turbo (within 1-2 feet or so). It won't open at idle and it will cause a little surge (a little delay to open) but it won't cause MAF issues when vented to atmosphere much either.

09-08-2020, 07:10 AM	#1
Dustyx77 Join Date: Mar 2020 Location: Norway Age: 23 Posts: 3 Trader Rating: (0) Feedback Score: 0 reviews	The blow off valve issue Hey guys, sooo I've bought a 200sx (eurospec) s14 that used to run on 24psi of boost, but the blow off valve, atleast according to the internet, is rated for 26psi. Sooo long story short, the car has still some major compressor surge sounds. I barely use full throttle because I use the car on the street. What kind of psi blow off valve spring would you guys suggest?

12-16-2020, 09:27 PM	#4
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,648 Trader Rating: (17) Feedback Score: 17 reviews	The correct type of bypass for a turbo will hang open at idle, like the stock bov. The best thing for the turbo is to be able to instantly relief any air, from using a very easy to open bov style. The reason people don't like to use the correct type of bov on their cars is often because they do not have a recirculated bov style. In other words, you need the bov to recirculate the air back to the intake (pre turbo) just like FACTORY does, or else, the maf will dump extra rich fuel into the engine whenever the bov opens. I suggest looking at the factory bov setup, the bypass style. See if you can get a BYPASS style bov. For example greddy type-s was a bypass style bov. Always put the bov as close to the turbo as possible. Never put it after an intercooler either. If you get bypass style bov, you can use a very easily to open bov, so the turbo will never be in pain. If you cannot get the bypass style, then the best alternative solution (used to be) is HKS SSQV placed right near the turbo (within 1-2 feet or so). It won't open at idle and it will cause a little surge (a little delay to open) but it won't cause MAF issues when vented to atmosphere much either. __________________ 5.3/4l80e/turbo 240sx playthrough: https://tinyurl.com/turbo240

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09-13-2020, 06:39 AM	#2
S14rebuild BANNED Join Date: May 2019 Location: Florida-FAIL Posts: 2,497 Trader Rating: (8) Feedback Score: 8 reviews	If ur getting surge then the bov isnt opening or its too small. First check your vacuum line to it. Should be a direct feed from intake manifold to the bov, not "teed" off another line. Then make sure it acually opens, not stuck or damaged.